Separation of toner particles from carrier liquid is important in various applications of electrophotography. Various types of separation apparatus are known in the patent literature. For example, there is described in U.S. Pat. No. 4,737,268 apparatus for electrostatically separating particles in a liquid stream. The technique of U.S. Pat. No. 4,737,268 is essentially a plating operation and thus requires periodic deplating in order to operate.
There is described in U.S. Pat. No. 4,504,138 a method and apparatus for developing electrostatic latent images wherein a thin highly viscous layer of concentrated toner particles is defined on a roller, portions of the layer being transferred to an image bearing surface by electrostatic means.